Internal fuse for transformer

ABSTRACT

A fuse holder assembly which is particularly adapted to be utilized in conjunction with the protection system for the primary side of a transformer assembly wherein the fuse holder is mounted on a plate, the plate being supported on the face of the transformer casing. The fuse holder extends from the plate through an aperture in the transformer housing such that the fuse is supported below the level of cooling fluid within the transformer housing. The assembly of the present invention is suitable for use in connection with any type of fuse and also the transformer assembly includes a protective cover which encloses the area on which the plate is mounted to render the system tamper-proof.

United States Patent 1 Risk 1 1151 3,701,926 14 1 0ct.3l, 1972 [54]INTERNAL FUSE FOR TRANSFORMER [72] Inventor; Jerry Risk, Versailles, Ky.

[7 3] Assignee: Kuhlman Corporation, Troy, Mich. 221 Filed: Jan. 20,1972 211 Appl. No.: 219,388

[52] u.s.c1....,.. .1 ..317/1 s,337/2o4 [511 1111.01. ..H02h 7/04 [58]FieldofSearch ..317/1s;337/204 [5 6] References Cited UNITED STATESPATENTS 3,0l4,l58 12/1961 Nelson etal ..317/1s- 3,435,291 3/1969 1Paulus., 317/1s Primary Examiner-James D. Trammell Attorney-Harness,Dickey & Pierce [57] ABSTRACT A fuse holder assembly which isparticularly adapted to be utilized in conjunction with the protectionsystem for the primary side of a transformer assembly wherein the fuseholder is mounted on a plate, the

plate being supported on the face of the transformer casing. The fuseholder extends from the plate through an aperture in the transformerhousing such that the fuse is supported below the level of cooling fluidwithin the transformer housing. The assembly of the present invention issuitable for use in connection with any type of fuse and also thetransformer assembly includes a protective cover which encloses the areaon 1 which the plate is mounted to render the system tamper-proof.

10 Claims, 3 Drawing Figures 1 INTERNAL FUSE FOR TRANSFORMER BACKGROUNDAND SUMMARY'OF THE v DEVELOPMENT This invention. relates generally to aprotective system for a transformer assembly and more particularly to afuse assembly for a ground mounted transformer. I

In the recent past, the use of ground supported transformer assembliesin home subdivisions has become more and more'prevalent due to thedesire to avoid overhead lines and interconnect the transformer with theuser by means of underground cables. These transformer assemblies aremounted adjacent. junctions of various property lines to afford a meansby which a ground level transformer may be inconspicuously mounted toprovide electrical service for several homes withlthe area. This trendhas decreased the problems of accessability inservicin'gtr ansformers ofthis type but has increased the possibility of unauthorized tamperingwith the transformer assembly. Further, a ground mountedtransformerlends itself to a more simple fusing arrangement due to thefact that the fuse assembly does not have to be available formanipulation by a hotstick, with the attendant complex mechanismnecessary for insuring that the fuse is mounted below the level of thecooling fluid within the transformer.

Further, it has been found desirable to provide a transformer with afusemounting assembly which is capable of receiving substantially all of thedifferent types of fuses being marketed for this purpose. Thus, theowner of the transformerassembly can take-advantage of competitivepricing by interchanging various types of fuses within any single typeof transformer housing. 1

Ground mounted transformer assemblies have been the subject of otherpatents, forexample, the Nesson et shaped bracket being fixidlyconnected to a closure al U.S. Pat. No. 3,014,158, issued Dec. 19, 1961,

wherein the transformer housing is mounted on a concrete pad and accessdoors are provided to render theconnection points and service panel ofthe transformer assembly tamper-proof yet relatively accessible to anauthorized serviceman. However, this transformer assembly uses arelatively complex fuse holder which is adaptedto be rigidly mounted onthe transformer housing and wherein a fuse is received within theconfines of a tubular housing supported such that a portion thereof isbelow the level of the cooling fluid.

Moreover, this assembly requires a particular type of fuse and isrelatively expensive to install. Further, the

servicepersonnel changing the fuse does not have any simple access tothe interior of the transformer housing whereby the fluid level of thetransformer may be checked simultaneously with replacement of the fuse.Under these circumstances it is possible that the fluid level within thetransformer will not be checked at'the time that the serviceman isreplacing a fuse.

The'assembly of the present invention, in the illustrated embodiment,contemplates the use of a standard type transformer housing whichincludes a primary and secondary coil mounted in magnetic couplingrelation by. means of a transformer core. The transformer is mounted ona concrete pad and includes a panel section which mounts the highvoltage and low voltage terminals. Also, a punched aperture is formed inthe panel section to provide access to the interior of the transreadilyaccessible to service personnel who are authorized to have access'to thepanel.

The fuse assembly, in the preferred embodiment, includes a generally Zshaped bracket which supports a connection terminal for interconnectingone end of the fuse and one end of the primary winding. The other end ofthe fuse is connected to the exterior terminal, the Z plate which ismounted on the exterior of the panel in closing relation to the aperturepunched in the panel. The fuse leads are of sufficient length such that,when the access plate is removed, the fuse holder assembly maybe removedfrom the interior of the transformer housing to a position wherein thefuse itself is approximately four or more inches out of the confines ofthe transformer housing. When the serviceman has removed the fuse holderassembly from the interior of the transformer housing, it will bereadily apparent to the serviceman whether the cooling fluid levelwithin the transformer housing is of sufficient height to insure thatthe fuse is immersed when properly positioned within the transformerhousing. Experience will tell the service personnel what is a properlevel for the cooling fluid or the proper level may be marked on aportion of the fuse holder assembly. Thus, any time the fuse isreplaced, or if the fuse is to be removed for any other purpose;including checking cooling fluid level, the fluid may be checked by theservice personnel without a great deal of effort. s t

Further, the access aperture in the transformer housing may bepositioned above the cooling fluid level to insure that no leakageoccurs when the fuse is removed. Also, the position of the accessaperture permits location of the fuse near the high voltage lead-in, adesirable position for the fuse. The design of the present inventionalso eliminates the need for a hand hole in the top of the transformerhousing assembly, which hole would necessitate the use of a false coverfor satisfac to ry appearance and tamper-proofing.

Accordingly, it is one object of the present invention to provide animproved fuse mounting assembly.

' It is another object of the present invention to provide an improvedfuse mounting assembly which is particularly adaptable to be utilized inconjunction with ground supported transformer assemblies.

It is a further object of the present invention to provide an improvedfuse mounting assembly which is particularly suited for tamper-prooftransformer assemblies.

It is still a further object of the present invention to provideanimproved fuse assemblywhich inherently permits the operator to check theoil level within the transformer assembly.

It is still a further object of the present invention to provide animproved fuse mounting assembly which is particularly adaptable toinsure that the fuse is supported below the cooling fluid level withinthe transformer assembly.

It is still a further object of the present invention to provide animproved fuse mounting assembly which It is still another object of thepresent invention to provide an improved fuse mounting assembly which isadapted to mount various types of fuses being sold for this purpose. I

It is still a further object of the present invention to provide animproved fuse mounting assembly which does not require the use of ahotstick in order to extract the fuse from the interior of the housingassembly.

It is another object of the present invention to provide an improvedfuse mounting assembly which permits location of the fuse near the highvoltage lead-in.

A further object of the present invention is to provide an 1 improvedfuse mounting assembly which eliminates the need for a hand hole in thetop of the transformer housing assembly, and thus obviates the necessityfor a false cover to cover the hand hole.

It is a further object of the present invention to provide an'improvedfuse mounting assembly which is inexpensive to construct, reliable inuse, and extremely simple to install. r

Further objects, features and advantages of this inventibn will becomeapparent from a consideration of the following description, the appendedclaims and the accompanying drawings in which:

FIG. 1 is a perspective view of a transformer assembly incorporating thefeatures of the present invention and particularly illustrating mountingthe cover plate of the fuse assembly on the panel;

FIG. 2 is a side view, partially in cross section, illustrating thedetails of the fuse mounting assembly incorporating the features of thepresent invention; and

FIG. 3 is a top view of the fuse mounting assembly of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 1 there isillustrated a transformer assembly which particularly illustrates aground mounted transformer assembly. The assembly 10 includes a pouredor preformed concrete pad 12 to provide the means on which the groundlevel transformer is permanently mounted. A cavity (not shown) in thepad is provided with suitable conduits affording means-through whichunderground power supply and service lines are led to and from anaccessible compartment 14 of the housing 16.

The ground level transformer 10 comprises an inaccessible sealed weldedsteel compartment 20 within which a transformer 22 is mounted (see FIGS.2 and 3). The interior of the housing 16 is filled with a cooling fluid,preferably oil as is common in the art, to cool the transformer andother elements mounted within the housing 16. The level of this coolingfluid is illustrated at 24 in FIG. 2. Also, a hingidly mounted door 28is provided to form a closure for the accessible compartment- 14 of thetransfonner housing 16. A lock is provided for the door 28, the lockbeing adapted to engage the element 30 to preclude unauthorized accessto the compartment 14 which contains the high voltage lines and otherservice features.

In studying the view of FIG. 1, it will. be noted that the accessiblecompartment 14 is generally divided into a high voltage and low voltagesection, the high voltage section being generally to the left on a panelplate 34 and the low voltage section generally being to the right onpanel 34. The system includes a pair of high voltage bushings 36,38 thatextend through the panel 34 of the compartment 14, each bushingincluding a conductor having one end disposed within the transformerhousing 16 and inaccessible to either authorized or unauthorizedpersons, the other end of the conductor being mounted within thebushings 36, 38. The high voltage section also includes a parking stand40 to accommodate primary termination accessories which are installedeither vertically or may be canted any angle to accommodate the tilt ofthe high voltage bushings. Further, the high voltage section includes anaccess plate 46 which mounts the novel fuse assembly to be describedmore particularly hereinafter.

Referring to the low voltage section, there are provided porcelainexternally clamped secondary bushings 48, 50 which are externallyclamped for fast and easy replacement. A pair of blades 52, 54 aretilted at a 60 degree angle from the vertical as is common in the art.The low voltage section further includes a stainless steel low voltageneutral blade 60 which is welded on to the tank. An insulated andexternally grounded neutral may be provided as an option. Thetransformer assembly further includes a pair of ground pads 62, 64, thepads being located close to the high voltage terminations for convenientgrounding of the cable concenm'c neutral and tank. A third grounding padand strap may be supplied when insulated low voltage bushing isrequired. The compartment 14 also includes a drain port 68 which isadapted to remove the cooling fluid from the interior of the housing 16.Further, an oil fill and pressure vent plug70 is provided adjacent thetop of the panel 34 and the plug may be used to vent internal pressurebefore opening the transformer tank.

The transformer tank may be opened by removal of an oil level plug 72which may be used to provide a point of routine oil level inspection.However, as will be seen from a further description of the featuresofthe present invention, the oil level inspection may be made inconjunction with replacement of fuses without the necessity of openingthe plug 72. Further, a greater area of visual inspection may beafforded by the removal of the plate 46.

Referringnow particularly to FIGS. 2 and 3, there is illustrated thespecific details of the high volt fuse assembly of the presentinvention. As seen from FIGS. 2 and 3, the housing 16 is provided withan aperture 76 which may be punched in the sheet metal fonning the frontplate of the transformer housing 16. The aperture is closed by means ofa gasket 78 and the plate 46 described in conjunction with FIG. 1. Theplate at 46 is fastened to the front panel by means of a plurality ofstuds 80. A fuse mounting assembly 82 is mounted to the plate 46 anddepends therefrom such that the major protion of the fuse holderassembly is submerged below the level 24 of the cooling fluid within thetransformer housing.

Basically, the fuse holder assembly includes a generally Z shapedbracket 86 which is stamped and formed of sheet metal. The bracket iswelded, at its upper end, to the plate 46 and the lower end is providedwith an aperture which is adapted to receive a bolt 88. The bolt 88 isutilized to fasten a bracket arm 90 to the lower end of the bracket 86,and bracket 90 forms an insulated support and connection assembly for afuse 92.

The lower end of the fuse is interconnected with one lead 94 of theprimary winding and the lower conductor 96 by means of a second boltassembly 98. The upper end of the fuse 92, including conductor'l00, isconnected to the input bushing 36 by means of a further connectorassembly 104. Thus, the electrical path from the primary windingincludes conductor 94, conductor 96, this latter connection being madeby the bolt assembly 98, the fuse 92, and finally the conductor 100 aThe circuit for the particular transformer illustrated includes a strap100 which is fabricated of laminated aluminum to interconnect both highvoltage terminals 36, 38. In practice, the input to the particulartransformer in question maybe, for example, connected to bushing 38 andthe output to the next transformer down the line from the power supplyis derived from high voltage bushing 36. Thus, the strap 110 must carrythe entire current load being absorbed by the individual loadsdownstream, away from the generating plant, while the conductor 100merely has to carry the current being utilized by the particularresident connected to the transformer 10. Thus, the conductor 100 can beof substantially less cross sectional area than the strap When it isdesired to change the fuse 92, the nuts 80 are removed and the plate 46is moved away from the face plate of the transformer housing 16.Theplate 46 is moved sufficiently away from the face plate of housing 16 topermit the plate 46 to be tilted clockwiseas seen in FIG. 2. This willpermit the operator to move the vertical section of the bracket 86through the aperture 76 and ultimately remove the bracket 90 and fuse 92from the interior of the housing. It will be noted that the oil levelwill appear as a smear on the vertical section of the bracket 86. Theconductors 94 and 100 are of sufficient length to permit the entireassembly, including the bracket 90 and bolt assembly 98, to be removedat least four inches from the face plate 34,

the invention is susceptible to modification, variation and changewithout departing from the proper scope or fair meaning of the subjoinedclaims. v

What is claimed is:

1. In a transformer assembly having a housing with a panel, a windingsupported in said housing and cooling fluid within the housing forcooling the winding, the improvement comprising a fuse assembly forprotecting the winding against an excess electrical condition comprisingmeans defining an opening in the panel above the level of the coolingfluid, closure plate means attached to said opening defining means forclosing said opening, a fuse, and bracket means having a ribbon elementattached at one end thereof to said plate means, said fuse beingsupported by the other end of said ribbo l efi ment below the level ofsaid cooling fluid.

I e improvement of claim 1 wherein said panel is avertical panel.

v 3. The improvement of claim 1 wherein said fuse is removed from saidhousing when said plate means is detached from said opening definingmeans and removed therefrom a sufficient distance.

4. The improvement of claim 3 wherein said fuse in cludes a conductorattached thereto and is supported relative to said other end by saidconductor.

5. The improvement of claim 4 wherein said bracket assembly includes afurther bracket element attached at one end thereof to the other end ofsaid ribbon element and at the other end to said conductor forsupporting said fuse.

6. The improvement of claim 3 wherein said strip element is formedgenerally in a Z-shape including a cen tral portion, said centralportion being of sufficient length to submerge said fuse in the coolingfluid.

7. The improvement of claim 6 wherein the panel is vertically disposedwith said central portion generally parallel thereto, said housingincluding means for lockably enclosing said panel.

8. The improvement of claim 7 wherein said central portion provides anindication of the fluid level within the housing upon removal of saidcentral portion from said housing.

9. The improvement of claim 8 wherein said fuse is removed from saidhousing when said plate means is

1. In a transformer assembly having a housing with a panel, a windingsupported in said housing and cooling fluid within the housing forcooling the winding, the improvement comprising a fuse assembly forprotecting the winding against an excess electrical condition comprisingmeans defining an opening in the panel above the level of the coolingfluid, closure plate means attached to said opening defining means forclosing said opening, a fuse, and bracket means having a ribbon elementattached at one end thereof to said plate means, said fuse beingsupported by the other end of said ribbon element below the level ofsaid cooling fluid.
 2. The improvement of claim 1 wherein said panel isa vertical panel.
 3. The improvement of claim 1 wherein said fuse isremoved from said housing when said plate means is detached from saidopening defining means and removed therefrom a sufficient distance. 4.The improvement of claim 3 wherein said fuse includes a conductorattached thereto and is supported relative to said other end by saidconductor.
 5. The improvement of claim 4 wherein said bracket assemblyincludes a further bracket element attached at one end thereof to theother end of said ribbon element and at the other end to said conductorfor supporting said fuse.
 6. The improvement of claim 3 wherein saidstrip element is formed generally in a Z-shape including a centralportion, said central portion being of sufficient length to submergesaid fuse in the cooling fluid.
 7. The improvement of claim 6 whereinthe panel is vertically disposed with said central portion generallyparallel thereto, said housing including means for lockably enclosingsaid panel.
 8. The improvement of claim 7 wherein said central portionprovides an indication of the fluid level within the housing uponremoval of said central portion from said housing.
 9. The improvement ofclaim 8 wherein said fuse is removed from said housing when said platemeans is detached from said opening defining means and removed therefroma sufficient distance.
 10. The improvement of claim 9 wherein said fuseincludes a conductor attached thereto and is supported relative to saidother end by said conductor.